ATXMEGA256A3U Datasheet, PDF (21/116 Pages) ATMEL Corporation – 8/16-bit Atmel XMEGA A3U Microcontroller

XMEGA A3U
11. Power Management and Sleep Modes
11.1 Features
11.2 Overview
• Power management for adjusting power consumption and enabled functions
• 5 sleep modes:
– Idle
– Power-down
– Power-save
– Standby
– Extended standby
• Power Reduction register to disable clock and turn off unused peripherals in Active and Idle
mode
Various sleep modes and clock gating are implemented in order to tailor power consumption to
the application's requirement. This enables the microcontroller to stop unused modules to save
power.
All sleep modes are available and can be entered from Active mode. In Active mode the CPU is
executing application code. When the device enters sleep mode, program execution is stopped
and interrupts or reset is used to wake the device again. The application code decides when and
what sleep mode to enter. Interrupts from enabled peripherals and all enabled reset sources can
restore the microcontroller from sleep to Active mode.
In addition, Power Reduction registers provide a method to stop the clock to individual peripher-
als from software. When this is done, the current state of the peripheral is frozen and there is no
power consumption from that peripheral. This reduces the power consumption in Active mode
and Idle sleep mode and enable much more fine-tuned power management than sleep modes
alone.
11.3 Sleep Modes
11.3.1
11.3.2
11.3.3
Idle Mode
In Idle mode the CPU and Non-Volatile Memory are stopped, but all peripherals including the
Interrupt Controller, Event System and DMA Controller are kept running. Any enabled interrupt
will wake the device.
Power-down Mode
In Power-down mode all clocks, including the Real Time Counter clock source are stopped. This
only allows operation of asynchronous modules that does not require a running clock. The only
interrupts that can wake up the MCU are the Two Wire Interface address match interrupt, asyn-
chronous port interrupts and USB resume interrupt.
Power-save Mode
Power-save mode is identical to Power-down, with one exception, if the Real Time Counter
(RTC) is enabled, it will keep running during sleep and the device can also wake up from either
RTC Overflow or Compare Match interrupt.
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